JPS63309927A - Ferroelectric liquid crystal electrooptic device - Google Patents

Abstract

PURPOSE:To enable multi-division driving in a range not possible with a TN liquid crystal by modulating the pulse width of an inverted voltage to produce a medium contrast. CONSTITUTION:A panel for which chiral smectic C (SmC*) is utilized is formed to have a thin gap. One of two sheets of polarizing plates 10, 10 is aligned in the polarization direction to the molecular axis direction of the molecules in either of + or -theta states. Another sheet is placed similarly in the molecular axis direction or disposed with 90 deg. inclination. The optical transmittance converges to an intermediate state while oscillating if a sufficiently high DC voltage is impressed to such panel to put the molecules in either of the + or -theta states and AC is thereafter impressed to the liquid crystal 8. The liquid crystal molecules appear as if the molecules stop near the + or -theta states. Display etc., are executed by using such phenomenon. The multi-division driving with the simple matrix is thereby enabled and the number of driver ICs is greatly reduced. Since the device is the simple panel without using active elements, the large-capacity liquid crystal panel of the lower cost is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optical device using chiral smectic liquid crystal.

Liquid crystals are used in a variety of displays, and due to their excellent characteristics such as small and thin panels and low power consumption, they are often used to display clocks and calculators. The liquid crystal used is a thermodropink liquid crystal, which takes on various liquid crystal phases within a certain temperature range.

This liquid crystal phase is roughly divided into nematic (abbreviated as N), which does not have a layer, and smectic (hereinafter, referred to as Sm), which has a layer, depending on the presence or absence of a layered structure. Sm is further uniaxial smectic A
(SmA) and bicyclic smectic C (SmC).

FIG. 1 schematically shows the molecular arrangements of N, SmA, and SmC. a represents N, b represents SmA, and c represents SmC.

Furthermore, if the liquid crystal molecules have an asymmetric carbon and are not racemic, the liquid crystal phase will have a twisted structure.

In N, it is chiral nematic (N”) and SmC
This is chiral smectic C (SmC'').

In general, SmC'' not only has a patterned structure but also has a dipole moment in the direction perpendicular to the molecular axis and exhibits ferroelectricity.

Ferroelectric liquid crystals were developed in 1975 by Meyer (J, de, P.
hys, 36° 1975, 69) et al., and its existence was demonstrated.

The liquid crystal synthesized at that time was commonly called DOBAMBC (2-methylbutyl P-((P-n-decyloxybenzylidene)).
It is called ``amino'') and is still actively used in research on ferroelectric liquid crystals.

The molecular arrangement of SmC" can be schematically shown as shown in FIG.

The molecular axis is tilted by an angle θ with respect to the normal direction of the layer, and this angle is constant in all layers.

However, the azimuth angle φ changes little by little depending on the layer, and the molecular orientation has a helical structure.

The pitch of this spiral varies depending on the liquid crystal, but it is usually several μm.
There are many degrees.

When SmC'' is injected into a cell as thin as about 1 μm, the spiral structure disappears and the SmC layer becomes perpendicular to the cell substrate.

SmC" liquid crystal has an electric twin moment perpendicular to the molecular axis, so in a thin cell the twin moments are aligned parallel to the layers. When an electric field is applied upward and downward, The molecules take positions tilted ±θ with respect to the normal to the layer.

By utilizing birefringence, the two states of ±θ can be made to correspond to brightness and darkness, and can be used as electro-optical devices such as displays.

FIG. 3 shows a schematic diagram of a conventional electro-optical device using two polarizing plates.

This driving principle is based on C1ark and Lagerwall (A
ppl.

Phys Lett, 36.899.1980).

They further claimed that this driving principle has the following characteristics.

That is, high-speed response on the order of fil μsee (2) Memory performance (3) Desired threshold characteristics Among these characteristics, the fast response indicates a response on the order of μsec in our observation.

Furthermore, as they claim, there are thermostats that maintain that state even after the electric field is applied and the electric field is turned off.

However, the desired dark value properties were not obtained in our observations.

According to our data, Vth, Vsat is Vth
= 500 (mV) Vsat = 5 (V).

In driving using the voltage averaging method, etc., it is impossible to perform time division driving such that a voltage of Vsat=5V is applied to the selected point, and a voltage of 500 (mV) or less is applied to the non-selected point.

The purpose of the present invention is to present a new principle and method of time-division driving using SmC", and to enable multi-division driving in a range that cannot be achieved with TN liquid crystals.

The details of the present invention will be explained below with reference to Examples.

FIG. 4 shows an embodiment of a cross-sectional view of a panel using "SmC".

Compared to a normal panel structure, the gap is about 2 μm, which is much thinner (4 μm or less).

Also, one of the two polarizing plates is ±
The molecular axis direction of the molecule in one of the states of θ is made to coincide with the polarization direction, and the other one is placed in the same direction along the molecular axis or is placed at an angle of 90°.

When a sufficiently high direct current voltage is applied to this panel to bring the molecules into a state of either ±θ, and then alternating current is applied to the liquid crystal, the optical transmittance changes as shown in FIG.

As is clear from the figure, when alternating current is applied, the optical transmittance oscillates and converges to an intermediate state.As shown in Figure 7, when the frequency of alternating current is high and the voltage is low, the optical transmittance decreases. Changes in rates tend to be small. In other words, the relaxation time becomes longer.

In the present invention, the stable state of ferroelectric liquid crystal molecules is changed by applying a DC voltage, and then the relaxation time of the optical change is lengthened by applying an AC voltage, so that the liquid crystal molecules stop at a position close to the ±θ state. It becomes like this. The idea is to utilize this for display purposes.

In other words, it is considered that molecules to which an alternating current voltage is applied do not vibrate around b or b' in FIG. 5, but stop. The driving principle of the present invention is to utilize this state to perform display, etc.

Regarding this characteristic, panels subjected to -axis orientation treatment have a strong orientation force and quickly return to the initial orientation state, but PV
A-rubbing (PVA refers to polyvinyl alcohol) has a relatively weak orientation force, and was able to maintain the display state with alternating current voltage and obtain a good display.

In actual driving, one example of the driving waveforms applied to the liquid crystal is as shown in a and b in FIG. 18.

Of these waveforms, the selected pixels on the scanning electrode are turned on (whether they are turned off or turned on depends on the polarization direction of the polarizing plate, but here we assume that the lighted state is obtained by the waveform a in Fig. 18). The waveform a in FIG. 18 is applied to the pixel. The movement of the liquid crystal molecules at this time is caused by the high voltage Va
When p is applied, it moves to position a or a' in Figure 5, or a position close to that position, and then vibrates at position b or b' with an alternating current voltage of equal positive and negative amplitude. It will be done.

In this case, in order to select the frequency of the drive waveform, a high voltage Yap
The settings must be made so that the liquid crystal molecules can move sufficiently to positions a and a'.

Furthermore, since the relationship between response time and voltage shown in FIG. 8 is linear, the frequency can be increased by increasing the voltage.

Then, after applying a voltage capable of inverting the ferroelectric liquid crystal as described above, the frequency and amplitude of the alternating current voltage applied can be increased to a high value and the amplitude to be decreased (by doing so, the state of the liquid crystal molecules can be stably maintained).

An appropriate drive frequency and drive voltage Vap may be set within a range that does not deteriorate the display state depending on the type of drive element or the type of display (for example, fixed display or moving image display).

The drive circuit we used in the experiment was 0MO3 and 20V
It was driven at a driving voltage Vap of .

In addition to 0MO3, FET, bipolar transistor, T
It can be driven by circuit elements such as TL and VMO3.

FIG. 9 shows the response time as a function of temperature.

The response time decreases monotonically as temperature increases.

When the temperature rises and the response time becomes short, if the drive voltage or drive frequency remains the same as when it was at a low temperature, a display state with many flickers will result.

Therefore, to prevent this, ■ Lower the voltage as the temperature rises.

■ Increase the frequency as the temperature rises.

■ Set both voltage and frequency appropriately.

There are three methods mentioned above.

In the driving method according to the present invention using "SmC", the driving voltage and driving frequency are set so as to display sufficiently at low temperatures,
Temperature compensation can be achieved by controlling at least one of the frequency and voltage as the temperature increases.

If you want to automatically compensate the temperature by installing the sensor in the circuit,
It is easier to select the drive clock signal digitally with a switching circuit.

However, in order to select the frequency continuously (in an analog manner) so as to allow fine adjustment, it is necessary to change the oscillation source continuously, so frequency control has the disadvantage of complicating the circuit. Furthermore, in the case of frequency control, when the temperature decreases, the frequency must also be lowered, which causes the problem that scanning takes time and flickers occur. Although there is no such problem when using voltage control, it is necessary to consider the withstand voltage of the driver IC.

Next, examples of actual drive waveforms will be shown to explain the present invention in further detail.

FIG. 10 to FIG. 1) are examples of drive waveforms of the present invention.

It is considered that a voltage of ±1/3 Vap is applied when not selected.

In addition, in the figure, the suffixes β and d indicate lighting and non-lighting (either negative or positive can be used depending on the orientation of the polarizing plate)
This symbol corresponds to

In actual driving, scanning of lighting and scanning of non-lighting are repeated alternately and displayed, and which one of FIGS. 10 to 1) is displayed! Alternatively, the waveform of d may be used.

Therefore, the drive signal including lighting and non-lighting scans is the 15th
Shown in the figure.

φY...Common (scanning) selection signal φY...Common (scanning) non-selection signal φX...Segment (information selection signal φX...Segment (information) non-selection signal Similarly, FIG. The drive waveform shown in is a drive waveform based on an AC pulse.

Further, FIG. 15 shows an actual drive signal that alternately performs lighting scanning and non-lighting scanning.

FIGS. 16 and 17 show an embodiment in which the common next to the selected common is not lit, and when the selected common is lit, it is displayed depending on whether a signal of opposite polarity is input.

In the embodiment shown in FIG. 16, when the common next to the selected common is turned off, the pixels to which the signals φX and φX are applied are turned off with the magnitudes of 315 Vap and Vap, respectively. The voltage is applied in the direction such that

The voltage sufficient for the non-lighting state is at least Va.
, it is necessary to set the following.

Similarly, the embodiment shown in FIG. 17 is an example in which a voltage of ■ap+315 Vap is applied in the non-lighting direction for φX and φX in the non-lighting direction, contrary to the above.

FIG. 18 is a diagram showing the potential applied to the pixel in the case of the driving method in which lighting and non-lighting are alternately performed.

This driving method is a driving method in which black and white (lighting and non-lighting) are written in Z frames. FIG. 19a shows a signal that changes depending on the frame; for example, in the first half of the scan corresponding to the first frame, an image is written, and in the second half of the scan corresponding to the second frame, white is written. .

That is, in the first frame, a voltage that inverts the ferroelectric liquid crystal molecules to one stable state in which the display state becomes black is applied to the pixels that should be black corresponding to the display information.

In the second frame, the remaining pixels that should be white are made white by applying a voltage that inverts the liquid crystal molecules to the other stable state where the display state becomes white. Ferroelectric liquid crystals have memory properties. Therefore, the image is completed with the above two frames.

b in FIG. 19 is a scan selection signal for selecting the first scan line. Signals a and b in FIG. 18 change the pixels on the first scanning line selected by the signal S in FIG.
b shows the voltage applied to the pixel when it is white.

When the second signal in FIG. 19 is at the old gh level, male (lit) and white (not lit) are selected.

FIG. 20 is a diagram showing a change in the potential applied to a pixel in a driving method in which a common electrode selected next to the selected common is turned off.

The previous scan electrode and the scan electrode are selected by the signals shown in FIG. 21. In addition, a driving method in which all pixels on the next scanning electrode are turned on is also conceivable, which is the opposite of this method.

FIGS. 22 to 27 are diagrams showing waveforms when a voltage 1/4 of the applied voltage Vap during selection is applied when not selected, respectively.

1 for each lighting. A suffix of d is added to non-lighting. In actual driving, any combination of lighting and non-lighting signal sequences can be used. However, in this drive, among the pixels on the selected common, lit pixels are 1/2 Vap when not lit, and non-lit pixels are 1/2 Vap when lit.
voltage is applied.

In the embodiments shown in FIGS. 10 to 27, the Vap ±
Among the driving methods in which positive and negative voltages of 1/a are applied, a=3
．． This is an example in which a=4, and a driving method in which positive and negative voltages of 1/a are applied to -C is also conceivable. (However, a is any positive number).

Further, regarding the driving method for erasing the one ahead of the selected common electrode, a driving method in which a positive and negative voltage of 1/a of Vap is applied when not selected can be considered in the same way.

FIG. 28 shows an example of a driving method in which positive and negative voltages of 1/4 Vap are applied when not selected, and the pixel on the next scanning electrode is not lit.

Such a driving method enables multi-division, which cannot be achieved with a TN type LCD. According to the present invention, a large-capacity liquid crystal device can be realized using a simple matrix, and an inexpensive, high-quality electro-optical device such as a display can be realized.

When SmC'' is driven with the driving waveform described above, the optical transmittance is as shown in FIG. 29.

Positive/negative V is applied to the pixel on the selected electrode among the scanning electrodes.
When ap is applied, the liquid crystal molecules move to a or a' in FIG.
The lens rotates to the position at or close to that position, reaching the highest level of optical brightness and darkness.

The optical transmittance attenuates while oscillating due to the alternating current pulses that oscillate equally in positive and negative directions, but the attenuation is thickest immediately after the equal positive and negative alternating current pulses are applied (and after that it is almost no change.

When the number of divisions is large, the time during which scanning electrodes are selected becomes short and the non-selection time occupies most of the time.

In the case of the present invention, the scan '@scanning group is selected continuously (selected continuously so that when the scan control signal of one scan electrode falls, the scan control signal of the next scan electrode rises), When the number of divisions is n, and the -scanning time is to, the time t for selecting one scanning electrode is expressed as t,=t,/n.

Moreover, the time t8 which is not selected is It is.

The optical transmittance when an AC pulse is applied in the non-selected state oscillates as described above, but the magnitude hardly changes.

Since this state occupies most of the scanning time, the optical transmittance of this state is perceived by the human eye as pixel contrast.

Therefore, whether the number of divisions is large or small, the contrast remains constant.

In our measurements, in a panel that is currently capable of driving 256 divisions, the contrast did not change much from 8 divisions to 256 divisions.

This phenomenon of ``SmC'' is extremely suitable for multi-segment display, compared to the fact that as the number of divisions of a TN type liquid crystal display panel increases, there is no difference in effective voltage between selected points and non-selected points, resulting in a decrease in contrast. It shows that there is.

If the response of "SmC" is possible up to 10 μsec, the scanning electrode groups in the present invention are selected continuously, so the number of divisions is 10×2 (μ5 ec). However, 30 m5 ec is the time required for one scan.

Moreover, 2 in the denominator indicates that positive and negative voltages are taken during the selected time.

When the liquid crystal responds at the highest speed ever achieved in the world, it is possible to drive a panel with approximately 1500 divisions, and as mentioned above, the drive of the present invention ensures that there is no difference in contrast between 1500 divisions and 8 divisions. It is possible by law.

Here, another advantage of the present invention regarding contrast will be described.

When the cell gap is reduced to about 1 μm, SmC1 loses its helical structure and the layers are aligned perpendicular to the panel substrate. This is as stated before.

The fact that the layers are perpendicular to the substrate means that the liquid crystal molecules are horizontal to the substrate.

When the molecules in this state are driven by the driving method according to the present invention, they are in the states a, b', which are close to a, a' in FIG.
The molecules are considered to be approximately horizontal to the substrate.

Even when this state is viewed from various viewing angles, there is almost no change in contrast because the molecules are horizontal to the substrate.

On the other hand, in a TN type liquid crystal display panel, the liquid crystal is not completely horizontal to the substrate when not lit (in the case of positive display).
Depending on the viewing angle, it can be considered to be standing, resulting in crosstalk.

This is known as so-called viewing angle dependence.

The display according to the present invention using "SmC" does not have such viewing angle dependence.Just as multi-segmentation has completely changed the conventional wisdom, there is also no viewing angle dependence regarding contrast, and the contrast changes depending on the number of partitions. It can be said that the electro-optical device using ``SmC'' according to the present invention has ground-breaking characteristics such as:

Furthermore, one embodiment of the drive waveform according to the present invention is shown in FIG.

This drive waveform is displayed by scanning the drive waveforms shown in FIGS. 10 to 28 once or a finite number of times, and then maintaining the display in a high impedance state (with the drive circuit turned off). It shows the voltage change applied to the liquid crystal when the liquid crystal is turned on.

In FIG. 30, a indicates the scanning portion, and b indicates the high impedance state.

It is clear that the optical transmittance remains at the positions s and b' in FIG. 5 in the high impedance state because the optical transmittance hardly changes even in the high impedance state.

This memory property is long enough, and only when the display changes
All you have to do is scan.

The power consumption in the high impedance state is zero, which is an energy-saving type of drive, and is most suitable for image display where the display content does not change much, such as a fixed display.

An example of a drive waveform similar to this drive is shown in FIG. 31.

Similar to the driving method using high impedance shown in FIG. 30, after scanning is performed once or a limited number of times, the driving frequency is increased to maintain the display. If you increase the drive frequency, the 7th
As shown in the figure, the state of liquid crystal molecules can be maintained more stably.

In the drive shown in Fig. 30, which uses memory through high impedance, the molecular position becomes high impedance and gradually returns to the initial orientation state from the point at which the external regulating force disappears, but the memory property is even better. Become. The phenomenon of returning to the initial orientation state at high impedance increases as the orientation force becomes stronger, and as the temperature increases, the phenomenon increases.

Since the influence of temperature is particularly large, it is more reliable to maintain the display by increasing the driving frequency as shown in FIG.

In the case of the drive shown in FIG. 31, scanning can be carried out as usual and only the driving frequency needs to be increased, and on the signal electrode side, display data can be output as is, or it can be set to either turn on or not turn on.

Whether the liquid crystal has a positive dielectric anisotropy △ε or a negative one, by increasing the driving frequency, the state of the molecules can be held more stably, and as a result, the image quality can be improved. . In particular, when a negative liquid crystal is used, the application of a high frequency voltage applies dielectric torque to the liquid crystal molecules that causes them to stagnate, which also has the effect of improving contrast.

Next, FIG. 32 shows an embodiment of a drive similar to that shown in FIG. 31.

The difference from the drive shown in Fig. 31 described above is that after one or a finite number of scans, the AC pulse with equal positive and negative voltages applied when not selected or the AC pulse with equal positive and negative voltages of different values. The point is that the display state is maintained by applying pulses.

FIG. 32 shows a drive waveform applied with an AC pulse of ±1/3 Vap.

In this embodiment, the driving waveforms applied to the scanning electrodes and the signal electrodes after scanning are equal amplitude waveforms with different phases as shown in FIG. 33.

In this case, the scanning electrodes are not scanned, and regardless of the data, the power waveform shown in FIG. 33 is applied to the scanning electrodes, and the other waveform is applied to the signal electrodes.

FIG. 34 shows an example of the voltage applied to the liquid crystal when using a driving method in which the voltage is set to zero volts after a finite number of scans.

Next, an embodiment of the driving method according to the present invention for obtaining gradation display will be described.

The basic method for grayscale display is to create halftones by modulating the ±Vap pulse width applied to pixels on selected scanning electrodes.

Paying attention to the change in optical transmittance during driving shown in FIG. 29, when the selection voltage ±Vap is applied, the brightness and darkness reach the highest level. After that, it attenuates, but after a sufficient amount of time has passed, the optical transmittance when the attenuation is almost gone is proportional to the magnitude of the optical transmittance when the selection voltage ±Yap is applied. was observed.

Utilizing this phenomenon, gradation display is possible by selectively adjusting the optical transmittance.

Since an optical transmittance proportional to the pulse width of the selection voltage ±Yap can be obtained, gradation display can be realized by this method.

Examples of drive waveforms are shown in FIGS. 35 to 47.

Each will be explained below.

FIG. 35 shows an example of a waveform to which the suffix i in FIG. 10 is attached, that is, a waveform used for lighting scanning, which is modified for gradation display.

The only difference between FIG. 35 and FIG. 1O is the segment selection signal, and the other signals may be the same.

In the embodiment, the selection voltage Vap is modulated by shifting the phase by τm.

The pulse width τap to which the selection voltage Vap is applied is τap!, where vA is the dynamic frequency f. The gradation is performed by adjusting τm according to the intermediate tone level.

FIG. 36 shows an example of the voltage actually applied to the liquid crystal from the signal shown in FIG. 35.

In Figure 36, a shows the waveform applied to the liquid crystal when the scanning electrode is selected and a selection signal is applied to the display electrode, and b shows the waveform when the scanning electrode is not selected and a non-selection signal is applied to the display electrode. It is a waveform. Contrary to b, C is a waveform when the scanning electrode is not selected and a selection signal is applied to the display electrode.

The time to take ±1/s Vap for both b and c is b,
They are considered to be equal within c.

Similarly to FIG. 35, FIG. 37 also shows a waveform obtained by changing the signal for non-lighting scanning in FIG. 11 for wjt tone display.

The difference from FIG. 35 is that the segment selection signal has a stepped waveform. Selection voltage applied to liquid crystal - Y
The pulse width of ap is narrowed by τm, and gradation display is performed by adjusting τm in accordance with the intermediate tone level.

In addition, FIG. 38 shows the waveform applied to the liquid crystal in the same way as FIG. 36. In the diagram, a, b, and c indicate the same states as in FIG. It has a waveform.

FIGS. 39 to 41 show an example in which the drive waveform to which an AC pulse with an amplitude of 1/3 Vap is applied when not selected is changed for gradation display.

All that needs to be changed is the segment selection signal, similar to the above.

There are two patterns to change.

There are two cases: a step-like case as shown in FIGS. 39 and 41, and a case where the phase changes as shown in FIG. 40.

Next, FIGS. 42 to 4 show examples in which the drive waveform, which becomes AC with an amplitude of 1/4 Vap when not selected, is changed to one for gradation display.
It is shown in Figure 7.

Similar to the gradation display described above, there are two ways to change the waveform: a step-like waveform and a waveform with different phases.
Vap can be modulated by τm.

It was previously shown that there are generally two ways to change the segment selection signal to obtain a Wi-tone display.

That is, (11) Shifting the phase (2) Creating a step waveform An example of the step waveform (2) is shown in FIG. 48 for a general case.

The top two are staircase waveforms when the lights are on, and the bottom two are when the lights are off.

V, ,V, are the following voltages, respectively.

V+ = (1 (2/a) Vap) vz = (2/a) Vap a is an arbitrary number, and when not selected, V a (1/a) V a
An alternating current pulse of p is applied.

As described above, the electro-optical device according to the present invention using "SmC" is an epoch-making liquid crystal element that overcomes the limitations of conventional X-Y matrix type liquid crystal elements that do not use active elements. For example, multi-division driving can be performed using a simple matrix, the number of driver ICs can be greatly reduced, and since it is a simple panel that does not use active elements, an inexpensive large-capacity liquid crystal panel can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the molecular arrangement of N, SmA, and SmC. Figure 2 is a diagram schematically showing the molecular arrangement and single-molecule state of SmC'' around the helical axis.
FIG. 2 is a schematic diagram showing a molecular state and a conventional display principle as viewed from the substrate direction. FIG. 4 is a sectional view of an electro-optical device according to the present invention. FIG. 5 is a schematic diagram showing the molecular state in the electro-optical device according to the present invention. FIGS. 6 and 7 show changes in optical transmittance when an AC pulse voltage is applied immediately after applying a DC voltage. FIG. 8 is a diagram showing the relationship between response time and applied voltage. FIG. 9 is a diagram showing the relationship between response time and temperature. FIG. 10 to FIG. 1) are examples in which positive and negative alternating current pulses of 1/3 of the selection voltage Vap are applied during non-selection. Figure 14 shows the 10th ti! J
-1) Figures 1 and 2 show waveforms with the same polarity, whereas the signals are composed of alternating current pulses. Figure 15 shows
Actual φY, φY, φ that summarizes lighting scans and non-lighting scans
X. The φX signal is the combination of FIGS. 10 and 11, and the first
4 is a diagram shown in the case of FIG. 4. Figures 16-17
The figure shows an example of a driving method for erasing all pixels on a scan electrode one ahead of a selected scan electrode, in which positive and negative alternating current pulses of 1/3 Vap are applied when not selected. 18th
The figure shows the voltage actually applied between the liquid crystals when FIGS. 10 to 14 are used. FIG. 19 shows the control signal. Figure 20 shows the first
When the embodiments shown in FIGS. 6 to 17 are used, the voltage actually applied between the liquid crystals is shown. FIG. 21 shows the control signal. Figures 22 to 27 show 1/4 when not selected.
This is an example in which positive and negative alternating current pulses of Vap are applied. FIG. 28 shows 1/4 Va of the driving method for erasing all pixels on the scan electrode one ahead of the selected scan electrode.
This is an example in which positive and negative alternating current pulses of p are applied when not selected. FIG. 29 shows the change in optical transmittance when driven. FIGS. 30-32 are examples of the voltage applied to the liquid crystal when using driving methods such as floating after a finite number of scans, increasing the frequency, and applying full AC pulses. FIG. 33 shows the waveforms applied to the common and segment electrodes after the finite number of scans of FIG. 32. FIG. 34 shows an example of the voltage applied to the liquid crystal when a driving method with a finite number of scans and zero volts is used. FIGS. 35 to 41 show examples of drive waveforms when gradation is performed by modulating the selection voltage Vap, and positive and negative alternating current pulses of 1/3 Vap are applied when not selected. 42nd
Figures 47 to 47 show examples of drive waveforms in which positive and negative alternating current pulses of 1/4 Vap are applied when non-selected, and the selection voltage Vap is modulated to display gray scales. Figure 48 shows gray scale display. An example of a segment selection signal for 1...Dipole moment 2...Liquid crystal molecules 3.4.5...Polarization direction 6...Electrode 7...Alignment film 8...Liquid crystal 9...-Sealing agent 10...Polarized light Plate 11...More than liquid crystal molecules Fig. 1 α Fig. 1 b Fig. 1 C Fig. 2 a Fig. 3 Fig. 6 Fig. 7 Fig. 8 3Vop Fig. 15(b) Fig. 16 Fig. 18 Fig. 20 Fig. 22 fYb ---0 Drink b--11----------1-
−. Figure 24 Vap Spider' VaVap Figure 26 Figure 27 Figure 2S Possible - 1 -------------. Fig. 30 - Fig. 31 Fig. 33 Fig. 34 Fig. 35 Fig. 36 Fig. 40 Figure 46 -

Claims (4)

[Claims] (1) A polarizing plate, a scanning electrode group that is sequentially and periodically selected based on a scanning signal, a signal electrode group that faces this scanning electrode group and is selected based on an information signal, and a polarizer between these electrode groups. An optical change that occurs when the molecular arrangement of the ferroelectric liquid crystal changes when a reversal voltage of the same polarity that can reverse the stable state of the ferroelectric liquid crystal is applied. An electro-optical device that utilizes
A ferroelectric liquid crystal electro-optical device that produces halftones by modulating the pulse width of the inversion voltage. (2) The ferroelectric liquid crystal electro-optical device according to claim 1, wherein an alternating voltage that does not reverse the stable state of the ferroelectric liquid crystal is applied to the pixels on the non-selected scanning electrodes. (3) The ferroelectric liquid crystal according to claim 2, wherein the alternating current voltage that does not reverse the stable state of the ferroelectric liquid crystal has an application time of one or two times the application time of the reversal voltage, each of the voltages having the same polarity. Electro-optical device. (4) The ferroelectric liquid crystal electro-optical device according to claim 2, wherein the AC voltage that does not reverse the stable state of the ferroelectric liquid crystal is an AC pulse having equal positive and negative amplitudes.